1. Field of the Invention
This invention relates to compounds which inhibit cellular β-amyloid peptide release and/or its synthesis, and, accordingly, have utility in treating Alzheimer's disease.
References
The following publications, patents and patent applications are cited in this application as superscript numbers:                1Glenner, et al., “Alzheimer's Disease: Initial Report of the Purification and Characterization of a Novel Cerebrovascular Amyloid Protein”, Biochem. Biophys. Res. Commun., 120:885-890 (1984).        2Glenner, et al., “Polypeptide Marker for Alzheimer's Disease and its Use for Diagnosis”, U.S. Pat. No. 4,666,829 issued May 19, 1987.        3Selkoe, “The Molecular Pathology of Alzheimer's Disease”, Neuron, 6:487-498 (1991).        4Goate, et al., “Segregation of a Missense Mutation in the Amyloid Precursor Protein Gene with Familial Alzheimer's Disease”, Nature, 349:704-706 (1990).        5Chartier-Harlan, et al., “Early-Onset Alzheimer's Disease Caused by Mutations at Codon 717 of the β-Amyloid Precursor Proteing Gene”, Nature, 353:844-846 (1989).        6Murrell, et al., “A Mutation in the Amyloid Precursor Protein Associated with Hereditary Alzheimer's Disease”, Science, 254:97-99 (1991).        7Mullan, et al., “A Pathogenic Mutation for Probable Alzheimer's Disease in the APP Gene at the N-Terminus of β-Amyloid. Nature Genet., 1:345-347 (1992).        8Schenk, et al., “Methods and Compositions for the Detection of Soluble β-Amyloid Peptide”, International Patent Application Publication No. WO 94/10569, published 11 May 1994.        9Selkoe, “Amyloid Protein and Alzheimer's Disease”, Scientific American, pp. 2-8, November, 1991.        10Tetrahedron Letters, 34(48), 7685 (1993)        11Losse, et al., Tetrahedron, 27:1423-1434 (1971)        12Citron, et al., “Mutation of the β-Amyloid Precursor Protein in Familial Alzheimer's Disease Increases β-Protein Production, Nature, 360:672-674 (1992).        13Hansen, et al., “Reexamination and Further Development of a Precise and Rapid Dye Method for Measuring Cell Growth/Cell Kill”, J. Immun. Meth., 119:203-210 (1989).        
All of the above publications, patents and patent applications are herein incorporated by reference in their entirety to the same extent as if each individual publication, patent or patent application was specifically and individually indicated to be incorporated by reference in its entirety.
2. State of the Art
Alzheimer's Disease (AD) is a degenerative brain disorder characterized clinically by progressive loss of memory, cognition, reasoning, judgment and emotional stability that gradually leads to profound mental deterioration and ultimately death. AD is a very common cause of progressive mental failure (dementia) in aged humans and is believed to represent the fourth most common medical cause of death in the United States. AD has been observed in races and ethnic groups worldwide and presents a major present and future public health problem. The disease is currently estimated to affect about two to three million individuals in the United States alone. AD is at present incurable. No treatment that effectively prevents AD or reverses its symptoms and course is currently known.
The brains of individuals with AD exhibit characteristic lesions termed senile (or amyloid) plaques, amyloid angiopathy (amyloid deposits in blood vessels) and neurofibrillary tangles. Large numbers of these lesions, particularly amyloid plaques and neurofibrillary tangles, are generally found in several areas of the human brain important for memory and cognitive function in patients with AD. Smaller numbers of these lesions in a more restrictive anatomical distribution are also found in the brains of most aged humans who do not have clinical AD. Amyloid plaques and amyloid angiopathy also characterize the brains of individuals with Trisomy 21 (Down's Syndrome) and Hereditary Cerebral Hemorrhage with Amyloidosis of the Dutch Type (HCHW A-D). At present, a definitive diagnosis of AD usually requires observing the aforementioned lesions in the brain tissue of patients who have died with the disease or, rarely, in small biopsied samples of brain tissue taken during an invasive neurosurgical procedure.
The principal chemical constituent of the amyloid plaques and vascular amyloid deposits (amyloid angiopathy) characteristic of AD and the other disorders mentioned above is an approximately 4.2 kilodalton (kD) protein of about 39-43 amino acids designated the β-amyloid peptide (βAP) or sometimes Aβ, AβP or β/A4. β-Amyloid peptide was first purified and a partial amino acid sequence was provided by Glenner, et al.1 The isolation procedure and the sequence data for the first 28 amino acids are described in U.S. Pat. No. 4,666,8292.
Molecular biological and protein chemical analyses have shown that the β-amyloid peptide is a small fragment of a much larger precursor protein (APP), that is normally produced by cells in many tissues of various animals, including humans. Knowledge of the structure of the gene encoding the APP has demonstrated that β-amyloid peptide arises as a peptide fragment that is cleaved from APP by protease enzyme(s). The precise biochemical mechanism by which the β-amyloid peptide fragment is cleaved from APP and subsequently deposited as amyloid plaques in the cerebral tissue and in the walls of the cerebral and meningeal blood vessels is currently unknown.
Several lines of evidence indicate that progressive cerebral deposition of β-amyloid peptide plays a seminal role in the pathogenesis of AD and can precede cognitive symptoms by years or decades. See, for example, Selkoe3. The most important line of evidence is the discovery that missense DNA mutations at amino acid 717 of the 770-amino acid isoform of APP can be found in affected members but not unaffected members of several families with a genetically determined (familial) form of AD (Goate, et al.4; Chartier Harlan, et al.5; and Murrell, et al.6) and is referred to as the Swedish variant. A double mutation changing lysine595-methionine596 to asparagine595-leucine596 (with reference to the 695 isoform) found in a Swedish family was reported in 1992 (Mullan, et al.7). Genetic linkage analyses have demonstrated that these mutations, as well as certain other mutations in the APP gene, are the specific molecular cause of AD in the affected members of such families. In addition, a mutation at amino acid 693 of the 770-amino acid isoform of APP has been identified as the cause of the β-amyloid peptide deposition disease, HCHW A-D, and a change from alanine to glycine at amino acid 692 appears to cause a phenotype that resembles AD is some patients but HCHW A-D in others. The discovery of these and other mutations in APP in genetically based cases of AD prove that alteration of APP and subsequent deposition of its β-amyloid peptide fragment can cause AD.
Despite the progress which has been made in understanding the underlying mechanisms of AD and other β-amyloid peptide related diseases, there remains a need to develop methods and compositions for treatment of the disease(s). Ideally, the treatment methods would advantageously be based on drugs which are capable of inhibiting β-amyloid peptide release and/or its synthesis in vivo.